Coronavirus Disease 2019 Vaccine Effectiveness Against Severe Acute Respiratory Syndrome Coronavirus 2 Infection in the United States Before the Delta- and Omicron-Associated Surges: A Retrospective Cohort Study of Repeat Blood Donors

Vaccine effectiveness against acquiring SARS-CoV-2 infection in US blood donors was 88.8% (95% confidence interval, 86.2%-91.1%) during the period January-June 2021, which demonstrates the feasibility of using antibody testing of blood donors to monitor vaccine effectiveness over time. Background To inform public health policy, it is critical to monitor coronavirus disease 2019 vaccine effectiveness (VE), including against acquiring infection. Methods We estimated VE using self-reported vaccination in a retrospective cohort of repeat blood donors who donated during the first half of 2021, and we demonstrated a viable approach for monitoring VE via serological surveillance. Results Using Poisson regression, we estimated an overall VE of 88.8% (95% confidence interval, 86.2-91.1), adjusted for demographic covariates and variable baseline risk. Conclusions The time since first reporting vaccination, age, race and/or ethnicity, region, and calendar time were statistically significant predictors of incident infection.

Automated summary

The study demonstrated that the vaccine effectiveness against acquiring SARS-CoV-2 infection in US blood donors was 88.8% during the first half of 2021. The findings suggest that monitoring vaccine effectiveness over time using antibody testing of blood donors is feasible.